The long range goal of this proposal is to study the cell biology and biochemistry involved in the function of B cells as antigen presenting cells. We will focus our attention on two membrane glycoproteins that are known to be involved in this function, namely membrane immunogloblin and Ia-antigens. Furthermore we will attempt to gain information as to why activation of B cells seems to be important in allowing this cell to serve as an antigen presenting cell. As part of this investigation the mechanism by which Gamma-irradiation inhibits the antigen presenting cell capacity of these cells will be explored. We will also try and define other membrane glycoproteins or elements that might be involved in the antigen presenting capacity of B cells and in particular to evaluate the potential role of membrane proteases in the processing of certain antigens. Among the techniques that we plan to use to evaluate the role of Ig and membrane Iy in the antigen presenting capacity of B cells, we will purify these membrane glycoproteins and incorporate them into liposomes. These liposomes will either be utilized directly as antigen presenting units or they will be used as vehicles to incorporate these membrane molecules into other cell types in order to probe how they function in different cellular milieu.